Compound for preparing molds for metal castings



Patented May 10, 1 932 UNITED STA res; PATENT enonen 11. eonnsmrrn, or'zronoiv'ro, ONTARIO, cAivAnA COMPOUND FOR PREPARING MOLDS FOR METAL CA STIN GS I No Drawing. a

The principal objects of this invention. are:

to produce metal castings of a superior quality with smooth, clearly defined surfaces which will be extremely accurate reproduc- 6 tions of thepatterns, and which will be uni- 10 duction in the cost of molding the casting,

the danger of tearing and the prevention of injury to machine tools from encountering embedded mold materials.

A still further object .is to enable the production of cores and molds which will reduce ing during shrinkage.

An additional important object is to enable the reinforcement of frangible cores and molds made with insoluble bonds such as clay.

The principal feature of the invention consists in applying to a mold or coresurface, a composite fluid material which readily permeates the body of the mold or core and deposits upon the surface thereof a soft, compressible, bonded substance presenting a uniformly smooth surface which will result in V the production of smooth, clean castings, the liquid Vehicle of the coating being adapted to partially disintegrate soluble bonds of the mold or core materials, and to reinforce insoluble bonds.

A further and important feature consists in providing a liquid compound, having the above properties, which is non-explosive and non-combustible while being applied.

In the art of moldin and casting metals, many different forms 0% coatings for the-surface of the core or mold have been proposed,

exterior to start with, are hydroscopic, are easily chipped or broken, and resist the escape of gases which cause defects in'the castings. In some instances suchv hardening effect of increasing the tendency of castings to fracture during the shrinkage period. Further, such excessive protection of surfaces keeps them from burning and renders destruction and removal of the cores and molds difficult.

or cracking of the castbut many of these, while producing a smooth the fluid, form a coating of scribed. This coating is deposited by fil-. tration of the liquid so as to close all the .surface irregularities, leaving a smooth substance containing a suflicient amount of of the core surfaces also has the detrimental Application filed October 7, 1929. Serial No. 398,095.

In carrying the present invention into effect, a composite fluid substanceis produced malnly of carbon tetrachloride and a soft powdery. substance such as groundtalc, to- 7 gether with a small quantity of asoluble binder, such as linseed oil or rubber.

OFF-ICE. I 2

Carbon tetrachloride is non-inflammable and it may be diluted with a hydrocarbon such as gasoline or with coal oil to approximately 25% without becoming inflammable or explosive. It may also be diluted with other soluble fluids such as carbon bisulphid,

propyl alcohol or formaldehyde in various combinat ons and the use of the term hydrocarbon 1n the claims is to be construed as including the above named dilutents or mediums capable of imparting a solvent propertyto the carbon tetrachloride compound in proportion to the quantity used. lutedcarbon tetrachloride is preferably mixed nineteen parts thereof with one part b of a soluble binder for the filler material.

In this solution is placed a quantity of fine powdered material such as talc, soapstone, graphite or plumbago, silica, silicaflour, mica, flour of mica or in certain cases other material such as bronze, tin or. aluminum powder may be found desirable. The

above filler mediums may be classified generally as inert fillers and the use of the term inert in .the claims in defining the filler medium may be construed to include any one or combination of the above fillers and while tale is desirable as the filler agent the invention is not restricted to its use.

A suflicient quantity of such powdered filler material is incorporated into the liquid so that when assisted in suspension, by agitation, they will, with the rapid absorption of the liquid by the core or mold dippedinto the character debinder to hold it securely. It will be readily understood that the quantity of powdered The di- I sired thickness of the surface coating, and slnce the fluld-suspending medium is highly volatile and light the agitation of the com-' pound serves to maintain the powdered inert fillers in uniform suspension throughout the mass. It is to be-noted that carbontetrachloride alone is practically a non-solvent of the compound is very important as a carrying agent for the filler materials so that when a dry core or mold is dipped in the compound the light, highly volatile carbon tetrachloride content will be rapidly absorbed into the core body carrying with it the solvent therein in content and the powdered filler materials sus- I so that the filler materials pended therein, will be rapidlydeposited on the outer surface and particles of the core. A true filtra-' tion action is thus involved and the depth ofthe coating of filler materials will be determined mainly by the length of time it is submerged in the compound and the proportion of filler used.-

It will thus be seen that the carbon tetrachloride being highly volatile and quickly absorbed into the core will on exposure of the treated core to the atmosphere rapidly evaporate leaving the core ready for use in a very short space of time.

The coating when first deposited is preferably of a soft nature, but will harden through the action of the binder material relation to the time it is exposed to air. The chemical characteristics of the liquid vehicle is such as to attack the soluble binders of the core or mold material which are commonly used and a partial disintegration of these binders commences immediately upon application of the liquid compound.

The surface coating applied by filtration as described and which contains a binder material, ofisetsthe initial weakening of the soluble binders of the core and mold materials,

of the mold surfaces during pouring of the metal. The subsequent application of heat through the pouring of the metal completes the disintegration of the binder commenced by the solvent action of the liquid vehicle. The initial solvent action of the liquid vehicle in such cases somewhat increases the porosity of the cores and molds below the surface coating and assists the ready escape of gases produced during the pouring of the metal. Gas produced by the burning of the binder of castings.

and prevents rapid disintegrationthe surface filler material, will pass readily through the surface coating of the powdered talc, or other substance, and through the body of the core or mold to regular outlets.

In some instances cores or molds are produced with insoluble bindersand when such are used the compound fluid which contains a binder material permeates the core or mold and acts to strengthen both the surface and body of the. cores and molds.

The use of this surface treating method does not destroy the binder but adds a further binder and in addition deposits a soft, smooth exterior coating. Such application of a core binder by infiltration of the liquid vehicle into the "core or mold-produces a binder of a very delicate nature readily disintegrated during the subsequent application ofheat.

The application of this surface treatment to cores and molds can be very accurately controlled so as to enable any degree of surface protection required, by varying the thickness of the coating applied and also by v varying its density and the proportion. of binder material.

All filler material binders soluble in the liquid vehicle, are non-hydroscopic in character, consequently the cores and molds so treated when stored are immune to absorption of moisture which would otherwise ren-- der them unfit for use.

The present process produces a surface the hardening characteristics of which may be regulated so that if desired they may be kept soft for an extended period. Use of such a surfacing permits the filling of misfit core prints with a soft plug which is very valuable in preventing the formation .of fins on The compound herein described preferably dries upon the surface but does not harden quickly due to the peculiar qualities of the vehicle described, which gives quick penetration and though such surface dries readily, enough binder is preferably used so thatit does not powder and will not wash off in the pouring of the metal butremains more 'or less plastic.

In the treatment of cores and molds having :insoluble binders, theuse of filler material binders in this process may be directed to increase the strength of thebody of the mold or core as well as the outer surfaces.

In some instances it may be found desirable to apply a thin coating of tin to the inside of castings and to accomplish thisresult, the tin may be placed in the solution in finely powdered or even colloidal form and be deposited upon the core so that when the metal is poured it will fuse on to the sun face thereof.

Many variations in the application of the method of treatment herein described may be made, so long as the principal feature consists in applying a surface coating of the character described, to the cores or molds by filtration of a liquid substance which will be readily absorbed into the core or mold leaving a fine powdered bonded substance as an outer coating and will partially disintegrate soluble bonds and reinforce insoluble bonds in the core or mold.

What I claim as my invention is:

1. Compound for treating dry sand cores and molds comprising a compound containing carbon-tetrachloride and a finely powdered inert filler material suspended therein by agitation to be applied directly to the dry cores or molds or by dipping the latter thereinto.

2. Compound for treating dry sand cores and molds as claimed in claim 1 in which the carbon-tetrachloride is diluted by the application thereto of gasoline.

3. A compound for preparing dry sand cores and molds for casting, comprising a mixture containing carbon-tetrachloride, finely powdered inert filler material, and a binder for acting on said powdered material, said compound to be applied directly to the dry cores or molds or by dipping the latter thereinto.

4. A compound for preparing dry sand cores and molds as claimed in claim, 3 in which the binder for acting on the filler material comprises a quantity of linseed oil.

5. A compound for treating dry sand cores and molds in preparation for casting comprising a mixture composed of carbon-tetrachloride having incorporated therewith a hydrocarbon bond solvent, a finely powdered inert filler material, and a binder'for said filler material, the said compound being maintained in agitation during useto retain the filler material in suspension.

6. A compound for preparing dry sand cores and molds for casting, comprising a mixture composed mainly of carbon-tetra chloride and a finely powdered talc to be applied directly to the dry core or mold or by dipping the latter thereinto.

7. A compound for preparing dry sand cores and molds for casting, comprising a mixture containing carbon-tetrachloride diluted with a hydrocarbon acting as a bond solvent for the core and having a finely powdered inertfiller material held in suspension therein by agitation, the said compound to be applied directly to the dry core or mold or by dipping the latter thereinto.

8. A compound for preparing dry sand cores and molds for casting comprising, a carbon-tetrachloride hydrocarbon mixture in approximately nineteen parts, the hydro-- carbon content being a bond solvent of the core, a soluble binder approximately one part, and a finely powdered inert filler substance held in suspension therein, the said compound to be applied directly to the dry core or mold or by dipping the latter thereinto.

9. A compound for preparing dry sand cores and molds for metal casting, comprising a fluid composed ofcarbon-tetrachloride in approximately nine parts to act as a carrier, a hydrocarbon approximately one part to act as a bond solvent, and an inert finely powdered insoluble filler suspended therein to form a coating for the core or mold surfaces, the said compound being applied directly to the dry core or mold or by dipping the latter thereinto.

' GEORGE H. GOLDSMITH. 

